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1.
Thermoelectric Properties of <Emphasis Type="Italic">n</Emphasis>-Type Multiple-Filled Skutterudites
Filled skutterudites are prospective intermediate temperature materials for␣thermoelectric power generation. CoSb3-based n-type filled skutterudites have good electrical transport properties with power factor values over 40 μW/cm K2 at elevated temperatures. Filling multiple fillers into the crystallographic voids of skutterudites would help scatter a
broad range of lattice phonons, thus resulting in lower lattice thermal conductivity values. We report the thermoelectric
properties of n-type multiple-filled skutterudites between 5 K and 800 K. The combination of different fillers inside the voids of the skutterudite
structure shows enhanced phonon scattering, and consequently a strong suppression of the lattice thermal conductivity. Very
good power factor values are achieved in multiple-filled skutterudite compared with single-element-filled materials. The dimensionless
thermoelectric figure of merit for n-type filled skutterudites is improved through multiple-filling in a wide temperature range. 相似文献
2.
Ca
z
Co4−x
(Fe/Mn)
x
Sb12 skutterudites were prepared by mechanical alloying and hot pressing. The phases of mechanically alloyed powders were identified
as γ-CoSb2 and Sb, but they were transformed to δ-CoSb3 by annealing at 873 K for 100 h. All specimens had a positive Hall coefficient and Seebeck coefficient, indicating p-type conduction by holes as majority carriers. For the binary CoSb3, the electrical conductivity behaved like a nondegenerate semiconductor, but Ca-filled and Fe/Mn-doped CoSb3 showed a temperature dependence of a degenerate semiconductor. While the Seebeck coefficient of intrinsic CoSb3 increased with temperature and reached a maximum at 623 K, the Seebeck coefficient increased with increasing temperature
for the Ca-filled and Fe/Mn-doped specimens. Relatively low thermal conductivity was obtained because fine particles prepared
by mechanical alloying lead to phonon scattering. The thermal conductivity was reduced by Ca filling and Fe/Mn doping. The
electronic thermal conductivity was increased by Fe/Mn doping, but the lattice thermal conductivity was decreased by Ca filling.
Reasonable thermoelectric figure-of-merit values were obtained for Ca-filled Co-rich p-type skutterudites. 相似文献
3.
Jiong Yang L. Xi W. Zhang L. D. Chen Jihui Yang 《Journal of Electronic Materials》2009,38(7):1397-1401
We present an investigation of electronic structures and electrical transport properties of some filled CoSb3 skutterudites by combining ab initio projected augmented plane-wave calculations and Boltzmann transport theory with electron group velocity evaluated by the
momentum matrix method. The systems are studied in a 2 × 2 × 2 supercell of Co4Sb12 to reveal the effects induced by different filler atoms and their filling fractions. The temperature dependences of the Seebeck
coefficient and power factor are studied, and they are in good agreement with experimental data. Our results reveal an optimal
filling fraction for n-type filled CoSb3 skutterudites and related compounds for achieving the highest power factor values. 相似文献
4.
A thermopile sensor was processed on a glass substrate by electrodeposition of n-type bismuth telluride (Bi-Te) and p-type antimony telluride (Sb-Te) films. The n-type Bi-Te film electrodeposited at −50 mV in a 50 mM electrolyte with a Bi/(Bi + Te) mole ratio of 0.5 exhibited a Seebeck
coefficient of −51.6 μV/K and a power factor of 7.1 × 10−4 W/K2 · m. The p-type Sb-Te film electroplated at 20 mV in a 70 mM solution with an Sb/(Sb + Te) mole ratio of 0.9 exhibited a Seebeck coefficient
of 52.1 μV/K and a power factor of 1.7 × 10−4 W/K2 · m. A thermopile sensor composed of 196 pairs of the p-type Sb-Te and the n-type Bi-Te thin-film legs exhibited sensitivity of 7.3 mV/K. 相似文献
5.
Single-phase nanostructured bulk Yb0.2Co4Sb12 skutterudites have been prepared by combining a melt spinning technique with spark plasma sintering. The effects of a pre-annealing
process on the microstructure and phase composition of ribbon samples and bulk materials are investigated. After the pre-annealing
process, average grain size increases from 200 nm to 300 nm for ribbon samples and from 250 nm to 350 nm for bulk materials,
and nearly single-phase skutterudites have formed. Because of the nanostructure, the thermal conductivity of bulk skutterudites
notably decreases 25% at 800 K. As␣a result, the ZT values are improved compared with starting material prepared by the traditional method. 相似文献
6.
XianLi Su Han Li QuanSheng Guo Xinfeng Tang Qingjie Zhang Ctirad Uher 《Journal of Electronic Materials》2011,40(5):1286-1291
n-Type CoSb2.875−x
Ge0.125Te
x
(x = 0.125 to 0.275) compounds with different Te contents have been synthesized by a melt–quench–anneal–spark plasma sintering
method, and the effects of Te content on the structure and thermoelectric properties have been investigated. The results show
that all specimens exhibited n-type conduction characteristics. The solubility limit of Te in CoSb2.875−x
Ge0.125Te
x
is found to be x = 0.25. The solubility of Te in CoSb3 is increased through charge compensation of the element Ge. The room-temperature carrier concentration N
p of CoSb2.875−x
Ge0.125Te
x
skutterudites increases with increasing Te content, and the compounds possess high power factors. The maximum power factor
of 3.89 × 10−3 W m−1 K−2 was obtained at 720 K for the CoSb2.625Ge0.125Te0.25 compound. The thermal conductivity decreases dramatically with increasing Te content due to strong point defect scattering.
The maximum value of the thermoelectric figure of merit ZT = 1.03 was obtained at 800 K for CoSb2.625Ge0.125Te0.25, benefiting from a lower thermal conductivity and a higher power factor. The figure of merit is competitive with values reported
for single-filled skutterudites. 相似文献
7.
Kwan-Ho Park Jae-Yong Jung Soon-Chul Ur Il-Ho Kim 《Journal of Electronic Materials》2010,39(9):1750-1754
The thermoelectric properties of In-filled and Fe-doped CoSb3 (In
z
Co4−x
- Fe
x
Sb12) skutterudites prepared by encapsulated induction melting were examined. A single δ-phase was obtained successfully by subsequent
annealing at 823 K for 120 h. The Hall and Seebeck coefficients of the In
z
Co4−x
Fe
x
Sb12 samples had positive signs, indicating p-type conduction. The electrical conductivity was increased by Fe doping, and the thermal conductivity was decreased by In
filling due to phonon scattering. The thermoelectric properties were improved by In filling and Fe doping, and were closely
related to the optimum carrier concentration and phonon scattering. 相似文献
8.
G. D. Tang Z. H. Wang X. N. Xu Y. He L. Qiu Y. W. Du 《Journal of Electronic Materials》2011,40(5):611-614
The thermoelectric properties of indium (In) and lutetium (Lu) double-filled skutterudites In
x
Lu
y
Co4Sb12 prepared by high-pressure synthesis were investigated in detail from 4 K to 365 K. Our results indicate that In and Lu double
filling can remarkably reduce the thermal conductivity, and substantially improve the thermoelectric performance. A thermoelectric
figure of merit of ZT = 0.27 for In0.13Lu0.05Co4.02Sb12 was achieved at 365 K, being larger by one order of magnitude than that for CoSb3. It is thought that the large difference in resonance frequencies of the In and Lu elements broadens the range of normal
phonon scattering in the multifilled skutterudites, helping to achieve an even lower lattice thermal conductivity. This investigation
suggests that an effective way to improve the thermoelectric performance of skutterudite materials is to use In and Lu double
filling. 相似文献
9.
Indium-filled skutterudites are promising power generation thermoelectric materials due to the presence of an InSb nanostructure
that lowers the thermal conductivity. In this work, we have investigated thermoelectric properties of triple-filled Ba
x
Yb
y
In
z
Co4Sb12 (0 ≤ x, y, z ≤ 0.14 actual) compounds by measuring their Seebeck coefficient, electrical conductivity, thermal conductivity, and Hall
coefficient. All samples were prepared by a melting–annealing–spark plasma sintering method, and their structure was characterized
by x-ray diffraction and transmission electron microscopy (TEM). TEM results show the development of an InSb nanostructure
with a grain size of 30 nm to 500 nm. The nanostructure is present in all samples containing In and is also detected by specific
heat measurements. The Seebeck and Hall coefficients indicate that the compounds are n-type semiconductors. Electrical conductivity increases with increasing Ba content. Thermal conductivity is strongly suppressed
upon the presence of In in the skutterudite structure, likely due to enhanced boundary scattering of phonons on the nanometer-scale
InSb inclusions. The highest thermoelectric figure of merit is achieved with Ba0.09Yb0.07In0.06Co4Sb11.97, reaching ZT = 1.25 at 800 K. 相似文献
10.
Wilfried Wunderlich Yuichiro Motoyama Yuta Sugisawa Yoshihiro Matsumura 《Journal of Electronic Materials》2011,40(5):583-588
In the (Ti
x
,Zr
y
)Ni
w
Sn
z
quaternary system with a composition near (x + y):w:z = 1:1:1 the existence of the half-Heusler (HH) phase has been confirmed, where Ti and Zr occupy one of the three lattice
positions substitutionally. The goal of this study is to characterize the thermoelectric (TE) properties of such materials.
TE properties were measured at large temperature differences up to ΔT = 800 K, exhibiting Seebeck voltages of about ±50 mV corresponding to Seebeck coefficients above 0.07 mV/K, with the highest
value measured for the (Ti0.4Zr0.6)Ni0.9Sn1.1 composition. Fe and Mn doping could not improve these values further. Measurements under closed-circuit conditions showed
very high currents of 0.4 mA for specimens at this particular composition. According to the composition, interfaces between
full-Heusler and HH phases are responsible for an electron pull-out phenomenon due to the electric field at their interfaces.
First-principle calculations of the electronic band structure confirm this explanation for why (TiZr)NiSn and CrNiSn are p-type TEs whereas NbNiSn is an n-type TE. These considerations will be useful in the search for other such systems. 相似文献
11.
Thermoelectric materials are attractive since they can recover waste heat directly in the form of electricity. In this study,
the thermoelectric properties of ternary rare-earth sulfides LaGd1+x
S3 (x = 0.00 to 0.03) and SmGd1+x
S3 (x = 0.00 to 0.06) were investigated over the temperature range of 300 K to 953 K. These sulfides were prepared by CS2 sulfurization, and samples were consolidated by pressure-assisted sintering to obtain dense compacts. The sintered compacts
of LaGd1+x
S3 were n-type metal-like conductors with a thermal conductivity of less than 1.7 W K−1 m−1. Their thermoelectric figure of merit ZT was improved by tuning the chemical composition (self-doping). The optimized ZT value of 0.4 was obtained in LaGd1.02S3 at 953 K. The sintered compacts of SmGd1+x
S3 were n-type hopping conductors with a thermal conductivity of less than 0.8 W K−1 m−1. Their ZT value increased significantly with temperature. In SmGd1+x
S3, the ZT value of 0.3 was attained at 953 K. 相似文献
12.
S. Ceresara M. Codecasa F. Passaretti P. Tomeš A. Weidenkaff C. Fanciulli 《Journal of Electronic Materials》2011,40(5):557-560
A Bi-15 at.%Sb alloy, homogenized by equal channel angular extrusion (ECAE) at T = 523 K, has been treated just above its solidus temperature, causing segregation of a secondary Bi-rich phase at the grain
boundaries. This process results in an in situ composite. The thermoelectric properties of the composite have been measured in the range of 5 K < T < 300 K. The results are compared with those of the homogeneous alloy. The presence of a Bi-rich phase improves the Seebeck
coefficient at T < 50 K, and enhances the electrical conductivity by a factor of 1.4 at T = 300 K up to a factor of 3.4 at T = 50 K; unfortunately, the thermal conductivity also increases by about 50% in the same temperature range. As a result, the
figure of merit, Z, is slightly suppressed above T = 110 K, but increases at lower temperatures, reaching a peak value of 4.2 × 10−3 K−1 at T = 90 K. The power factor considerably increases over the whole temperature range, rendering this material suitable as the
n-type leg of a cryogenic thermoelectric generator for cold energy recovery in a liquefied natural gas plant. 相似文献
13.
Ge Nie Takahiro Ochi Shogo Suzuki Masaaki Kikuchi Satoru Ito Junqing Guo 《Journal of Electronic Materials》2014,43(6):1752-1756
By multifilling with La, Ba, Ga, Ti, Yb, Ca, Al, and In, the dimensionless figure of merit ZT of filled skutterudites has been improved in this work. ZT reached 0.75 for p-type (La,Ba,Ga,Ti) x (Fe,Co)4Sb12 (x = 0.8 to 1.0) and 1.0 for n-type (Yb,Ca,Al,Ga,In) y (Co,Fe)4Sb12 (y = 0.7 to 0.9). After annealing at 873 K for 180 h, 300 h, 710 h, 1000 h, and 5000 h in vacuum, the Seebeck coefficient S and the electrical resistivity ρ of the samples increased while the thermal conductivity λ decreased with increasing annealing time. As a result, the ZT values of both p- and n-type skutterudites remained unchanged or were slightly improved, demonstrating the excellent thermal stability of these skutterudites. 相似文献
14.
Polycrystalline p-type Bi0.5Sb1.5Te3 and n-type Bi2Te2.7Se0.3 thermoelectric (TE) alloys containing a small amount (vol.% ≤5) of SiC nanoparticles were fabricated by mechanical alloying
and spark plasma sintering. It was revealed that the effects of SiC addition on TE properties can be different between p-type and n-type Bi2Te3-based alloys. SiC addition slightly increased the power factor of the p-type materials by decreasing both the electrical resistivity (ρ) and Seebeck coefficient (α), but decreased the power factor of n-type materials by increasing both ρ and α. Regardless of the conductivity type, the thermal conductivity was reduced by dispersing SiC nanoparticles in the Bi2Te3-based alloy matrix. As a result, a small amount (0.1 vol.%) of SiC addition increased the maximum dimensionless figure of
merit (ZT
max) of the p-type Bi0.5Sb1.5Te3 alloys from 0.88 for the SiC-free sample to 0.97 at 323 K, though no improvement in TE performance was obtained in the case
of n-type Bi2Te2.7Se0.3 alloys. Importantly, the SiC-dispersed alloys showed better mechanical properties, which can improve material machinability
and device reliability. 相似文献
15.
An n-type mercury cadmium telluride (HgCdTe) unipolar nBn infrared detector structure is proposed as a means of achieving performance
limited by intrinsic thermal carrier generation without requirements for p-type doping. Numerical modeling was utilized to calculate the current–voltage and optical response characteristics and detectivity
values for HgCdTe nBn and p–n junction devices with a cut-off wavelength of 12 μm for temperatures between 50 K and 300 K. Calculations demonstrate similar dark current density, responsivity, and detectivity
values within 10% for the long-wavelength infrared (LWIR) nBn detector compared with the p–n junction structure for temperatures from 50 K to 95 K. These results show that the HgCdTe nBn device may be a promising alternative
for achieving high performance using a simplified device structure while circumventing issues related to p-type doping in current p–n junction technology such as achieving low, controllable doping concentrations, and serving as a basis for next-generation
device structures. 相似文献
16.
R. Wollrab A. Bauer H. Bitterlich M. Bruder S. Hanna H. Lutz K.-M. Mahlein T. Schallenberg J. Ziegler 《Journal of Electronic Materials》2011,40(8):1618-1623
Mainly driven by space applications, mercury cadmium telluride (MCT) focal-plane arrays (FPAs) have been successfully developed
for very long wavelengths (λ
CO > 14 μm at 55 K). For this purpose, the standard n-on-p technology based on MCT grown by liquid-phase epitaxy (LPE) and involving vacancy doping has been modified to extrinsic doping
by a monovalent acceptor. Due to the planar diode geometry obtained by ion implantation, most of the carrier generation volume
is located in the p-type region with a thickness of approximately 8 μm. According to our understanding, the Shockley–Read centers connected with the Hg vacancies are thus significantly reduced.
This situation should lead to longer minority-carrier lifetimes and smaller generation rates under equilibrium conditions,
therefore yielding lower dark current. We indeed observe a reduction by a factor of approximately 15 by using extrinsic doping.
Recent dark current data obtained in the temperature range from 55 K to 85 K on 288 × 384 FPAs with λ
CO(60 K) = 12 μm, either intrinsically or extrinsically doped, corroborate this finding. These data, new results on a 112 × 112 pixel demonstrator
array with λ
CO(55 K) = 14.4 μm, and earlier measurements are compared with Tennant’s Rule 07 established for p-on-n technology. 相似文献
17.
Single crystal diffraction measurements were successfully carried out for spherical fine grains grown as single crystals of
0.05–0.2 mm in diameter. Local modulations in the silicon layers were also observed by means of high-resolution electron microscopy.
The metallic tin–flux technique was used for crystal growth. The Fourier synthesis and maximum entropy method (MEM) were applied
to x-ray diffraction data to obtain electron density distribution maps. Mn4Si7 is one of the most promising p-type thermoelectrics useable from 400 K to 700 K. The crystal structure is described in terms of a chimney-ladder structure.
The doping effect, by which the system becomes n-type and a structure modulation occurs, was reported by our group previously. The resultant electron density maps were compared
with those from the band calculation. The MEM calculation shows the displacement of silicon positions. 相似文献
18.
P. Tomeš R. Robert M. Trottmann L. Bocher M. H. Aguirre A. Bitschi J. Hejtmánek A. Weidenkaff 《Journal of Electronic Materials》2010,39(9):1696-1703
Novel thermoelectric oxides were developed, produced, and characterized to demonstrate their promising thermoelectric conversion
potential in a thermoelectric converter. Four-leg thermoelectric oxide modules were fabricated by combining p- and n-type oxide thermoelements made of pressed polycrystalline GdCo0.95Ni0.05O3 and CaMn0.98Nb0.02O3, respectively. In these modules, the p- and n-type thermoelements were connected electrically in series and thermally in parallel. The materials were joined by electrical
contacts consisting of a Ag/CuO composite material. Fairly good thermal contacts were ensured by pressing the thermoelements
between alumina substrates. Cross-sections of the alumina/Ag–CuO mixture/thermoelement interface were investigated by scanning
electron microscopy. The temperature distribution across the module was monitored using K-type thermocouples and a micro-infrared
(IR) camera. The open-circuit voltage and the load voltages of the module were measured up to a temperature difference of
ΔT = 500 K while keeping the temperature of the cold side at 300 K. The output power and internal resistance were calculated.
The characteristics of the module evaluated from electrical measurements were compared with respective values of the p- and n-type leg materials. An output power of 0.04 W at ΔT = 500 K led to a power density of ~0.125 W/cm3, where the volume of thermoelectric material was determined by a cross-section of 4 mm × 4 mm and a leg length of 5 mm. 相似文献
19.
Wenhao Fan Ruixue Chen Liqi Wang Peide Han Qingsen Meng 《Journal of Electronic Materials》2011,40(5):1209-1214
The thermoelectric properties of Y-doped (1000 ppm, 2000 ppm, 3000 ppm) Mg2Si fabricated using field-activated pressure-assisted synthesis (FAPAS) have been characterized using measurements of electrical
resistivity (ρ), Seebeck coefficient (S), and thermal conductivity (κ) at temperatures ranging from 285 K to 810 K. The Y-doped Mg2Si samples were n-type in the measured temperature range. A first-principles calculation revealed that the Y atoms were expected to be primarily
located at Mg sites. In sample doped with 2000 ppm Y, which exhibited the best electrical and thermal conductivity, the absolute
value of the Seebeck coefficient increased in the temperature range of 320 K to 680 K, being higher than that of undoped Mg2Si. Moreover, this sample exhibited a higher level of electrical conductivity and a higher power factor. In addition, introduction
of Y decreased the thermal conductivity appreciably, indicating that Y dopants are favorable for improving the properties
of Mg2Si. 相似文献
20.
Y. Isoda S. Tada T. Nagai H. Fujiu Y. Shinohara 《Journal of Electronic Materials》2010,39(9):1531-1535
Mg2Si1−x
Sn
x
-system solid solutions are ecofriendly semiconductors that are promising materials for thermoelectric generators in the middle
temperature range. To produce a thermoelectric device, high-performance p- and n-type materials must be balanced. In this paper, p-type Mg2.00Si0.25Sn0.75 with Li and Ag double doping was prepared by the liquid–solid reaction method and hot-pressing. Effects of Li and Ag double
doping on thermoelectric properties were investigated in the temperature range from room temperature to 850 K. All sintered
compacts were identified as single-phase solid solutions with anti-fluorite structure. The carrier concentration increased
with the double doping. The temperature dependence of resistivity of the double-doped samples was similar to that of a metal.
The seebeck coefficient increased with temperature to a maximum value and then decreased in the intrinsic region. Thermal
conductivity decreased linearly with increasing temperature, reaching a minimum near the intrinsic region, and then increased
rapidly because of the contribution of the bipolar component. The dimensionless figure of merit reached 0.32 at 610 K for
Mg2.00Si0.25Sn0.75 double-doped with Li-5000 ppm and Ag-20000 ppm. 相似文献